Inductively Coupled Plasma Light Source with Direct Gas Injection

Abstract

An ultraviolet light source with direct feed gas injection includes a chamber comprising a plasma confinement region and defining an aperture adjacent to the plasma confinement region that passes light generated by the plasma. A magnetic core is positioned around the plasma confinement region and is configured to generate a plurality of plasma current loops that converges in the plasma confinement region during operation. A feed gas injector is coupled to a gas port in the chamber and has an output that is positioned proximate to a boundary of the plasma confinement region so that the feed gas injector provides a feed gas to the plasma confinement region that creates a differential pressure in the plasma confinement region. A high voltage region is coupled to the plasma confinement region. An exhaust port is configured to be coupled to a pump that controls a pressure in the chamber.

What is claimed is: 
     
         1 . An ultraviolet light source with direct feed gas injection, the light source comprising:
 a) a chamber comprising a plasma confinement region and defining an aperture adjacent to the plasma confinement region that passes light generated by the plasma;   b) a magnetic core positioned around the plasma confinement region and configured to generate a plurality of plasma current loops that converges in the plasma confinement region during operation;   c) a feed gas injector coupled to a gas port in the chamber and having an output positioned proximate to a boundary of the plasma confinement region, the feed gas injector providing a feed gas to the plasma confinement region that creates a differential pressure in the plasma confinement region;   d) a high voltage region coupled to the plasma confinement region; and   e) an exhaust port that is configured to be coupled to a pump that controls a pressure in the chamber.   
     
     
         2 . The light source of  claim 1  wherein the output of the feed gas injector is positioned within 1 cm of the boundary of the plasma confinement region. 
     
     
         3 . The light source of  claim 1  wherein the output of the feed gas injector is positioned within ½ cm of the boundary of the plasma confinement region. 
     
     
         4 . The light source of  claim 1  wherein the output of the feed gas injector is positioned between a low voltage region and the high voltage region of the chamber. 
     
     
         5 . The light source of  claim 1  wherein the feed gas injector comprises a gas tube having an output that is positioned proximate to the boundary of the plasma confinement region. 
     
     
         6 . The light source of  claim 1  wherein the feed gas injector is formed in the chamber. 
     
     
         7 . The light source of  claim 1  wherein the feed gas injector comprises a plurality of apertures that provide the feed gas into plasma confinement region. 
     
     
         8 . The light source of  claim 1  wherein the feed gas injector is positioned so that substantially all feed gas flows through the plasma confinement region before passing into the exhaust port. 
     
     
         9 . The light source of  claim 1  wherein the feed gas injector is positioned and configured so that a desired ratio of pressure in the plasma confinement region to pressure in the chamber proximate to the exhaust port is maintained during operation. 
     
     
         10 . The light source of  claim 1  further comprising a second gas injection port. 
     
     
         11 . The light source of  claim 10  wherein the second gas injection port is positioned proximate to the high voltage region. 
     
     
         12 . The light source of  claim 10  wherein the second gas injection port is positioned proximate to a low voltage portion of the chamber. 
     
     
         13 . The light source of  claim 10  wherein the second gas injection port is configured to introduce a second type of feed gas. 
     
     
         14 . The light source of  claim 10  wherein the second gas injection port comprises an output that is positioned proximate to a second boundary of the plasma confinement region. 
     
     
         15 . The light source of  claim 10  further comprising a second feed gas injector coupled to the second gas injection port and having an output positioned in the second boundary of the plasma confinement region. 
     
     
         16 . The light source of  claim 10  wherein the second gas injection port is configured to inject gas into the chamber at a location that provides a desired amount of back flow of gas into the plasma confinement region after formation of a pinch expansion in the plasma confinement region. 
     
     
         17 . The light source of  claim 10  wherein the second gas injection port is positioned to inject gas into the chamber so as to reduce self-absorption of the feed gas outside of the plasma confinement region. 
     
     
         18 . The light source of  claim 1  wherein the feed gas injector comprises a pulsed gas injector configured to inject gas into the plasma confinement region at times that refill the plasma confinement region after pinch expansion. 
     
     
         19 . A method of generating ultraviolet light, the method comprising:
 a) providing a chamber that defines a plasma confinement region therein, the chamber defining a port that passes plasma generated light out of the chamber, a high voltage region coupled to the plasma confinement region, and an exhaust port that is configured to be coupled to a vacuum pump that controls a pressure in the chamber;   b) directly injecting a feed gas into a boundary of the plasma confinement region;   c) providing voltage to the high voltage region, thereby generating a plasma; and   d) controlling a pressure in the plasma confinement region relative to the chamber so as to provide a desired pressure differential   
     
     
         20 . The method of  claim 19  wherein the controlling the pressure in the plasma confinement region relative to the chamber comprises controlling a flow of the feed gas with a mass flow controller. 
     
     
         21 . The method of  claim 19  further comprising injecting a feed gas in the chamber. 
     
     
         22 . The method of  claim 21  wherein the feed gas injected into the chamber is injected proximate to the high voltage region. 
     
     
         23 . The method of  claim 21  wherein the feed gas injected into the chamber is injected proximate to a low voltage region. 
     
     
         24 . The method of  claim 19  further comprising adjusting a flow of the feed gas injected into the chamber so as to provide a desired amount of back flow of gas into the plasma confinement region after formation of a pinch expansion in the plasma confinement region. 
     
     
         25 . The method of  claim 19  further comprising injecting a second feed gas directly into a second boundary of the plasma confinement region. 
     
     
         26 . The method of  claim 19  wherein the directly injecting the feed gas into the boundary of the plasma confinement region comprises injecting the feed gas through a tube having an output positioned inside of the boundary of the plasma confinement region. 
     
     
         27 . The method of  claim 19  wherein the directly injecting the feed gas into the boundary of the plasma confinement region comprises injecting the feed gas in a plurality of locations inside of the boundary of the plasma confinement region. 
     
     
         28 . The method of  claim 19  further comprising configuring the chamber so that substantially all the feed gas flows through the plasma confinement region before passing into the exhaust port. 
     
     
         29 . The method of  claim 19  further comprising pumping the chamber through an exhaust port to provide a desired ratio of pressure in the plasma confinement region to pressure in the chamber proximate to the exhaust port. 
     
     
         30 . The method of  claim 19  further comprising adjusting a flow of the feed gas directly injected into the boundary of the plasma confinement region so as to provide a desired ratio of pressure in the plasma confinement region to pressure in the chamber proximate to an exhaust port. 
     
     
         31 . The method of  claim 19  wherein the directly injecting the feed gas into the boundary of the plasma confinement region comprises injecting gas into the plasma confinement region at times that refill the plasma confinement region after pinch expansion. 
     
     
         32 . The method of  claim 19  wherein the directly injecting the feed gas into the boundary of the plasma confinement region comprises injecting the feed gas at a flow rate that reduces self-absorption of the feed gas outside of the plasma confinement region.